DIY gasket material for outdoor video cam?

[NeverDie]

Now that I'm nearly done pulling Cat6, I'll soon be installing this Hikvision turret outdoor videocam, which is PoE and can allegedly record 3MP video at 20fps.  Instructions for the physical installation don't seem to exist, but installation is fairly self-evident except with regard to sealing up the roughly 1-1/2" hole for cabling that the drilling template calls for. 
 
As I'm limited by file size to about one photo per post, I'll continue this narrative in the next post below...

 

[NeverDie]

Here's a shot from what will be the top after installation.  I'll be attaching it to an outdoor soffit.  The cabling will go through the 1-1/2" hole in the soffit.  In my case, the soffit material is Hardieboard, a 3/8" thick fiber cement board which, unlike wood, will never rot.
 
The camera itself is allegedly IP66.
 
 

 

[NeverDie]

Here's a photo showing a side view with the trim ring removed.
 
What you're now able to see is that there will be quite a gap between the soffit and the base, except for the three small points of contact on the base where screws will be holding the camera base tight against the soffit.
 
So, the question is: how best to seal this?  If this were a "once-and-done" installation that would last for decades, I'd probably reach for silicon caulk, or similar, to seal the gap.  However, there's no telling how long it will last.  In fact, the reason why I'm sprinting to install it now is to see whether it will survive the summer heat, because if it does, I'll probably get and install more.  My WAG is that it may last 3-5 years, but it may be far less than that.
 
Therefore, before even putting it up, I'm already thinking ahead to when I'll be taking it down for replacement.  When that day comes, as it surely will, I'd rather not be standing on a ladder 20 feet off the ground, cutting through silicon and eventually scraping it off prior to the next install.  Instead of that, what I'd much rather do is to fabricate a gasket of just the right thickness that will completely fill the gaps when when the 3 support screws are torqued down.  The gasket will be hidden by the trim ring, which would be installed afterward.
 
Has anyone here done this?  Also, what are good sources of sheet gasket material for this type of application?

 

[NeverDie]

My first thought is that a closed cell neoprene sponge rubber (basically what wet suits are commonly made from) would be a good choice for gasket material, because it has a serviceable temperature from -40F up to around 160F.  I would then just trim to fit with scissors.  If I'm lucky, I may find an old mouse pad of the right thickness that I can re-purpose into the gasket material.

 

[NeverDie]

Another option might be some kind of non-hardening waterproof putty.  Perhaps a non-oil based plumbers putty?  I actually have some already, left over from a garbage disposer installation, that's compatible with both plastic and metal.  I'll need to check the specs regarding temperature range, potential flammability, etc.
 
I also have some acoustical sealant, in caulk gun tubes, which is supposed to be non-hardening also.  I have doubt that it's waterproof, but I'll look into it.
 
DAP makes a removeable waterproof caulk, but the last time I checked it needs to be removed within a year before it transforms itself into a non-removeable caulk.  Therefore, it wouldn't be a good choice for this application.
 
Anyhow, through these examples, I've hopefully expressed at least notionally what the objective is.  Perhaps others here will know of a product that I haven't yet considered, or may not even know about, and that would be even more suitable.
 
Suggestions/recommendations are welcome.

 

[NeverDie]

It occurs to me now that I could probably adhere some closed cell backer rod or EPDM weatherstrip to the gaps on the camera base, and those could create a compression seal during installation when the screws tighten the base against the soffit.  It comes in a variety of thicknesses, and it's readily available.  Unlike a sticky non-curring putty or sticky non-curring sealant, there would be no cleanup of the soffit required in the future when the videocam is de-installed.  That means less acrobatics on a tall ladder, which is a win.
 
Unless someone here has a better idea--and soon--I'll likely go this route.
 
I've already pulled Cat6 all the way up to (but not through) the location for the bore hole through the Hardieboard soffit.  This Saturday I'm due to receive a proper hole saw for boring the hardieboard, so I'll likely attach the videocam to the soffit this Sunday, or soon thereafter.   i.e. I can't dither this topic much longer.   
 
/End monolog.

 

[RAL]

Electricians often use this stuff, called Duct Seal.  It's a heavy duty waterproof putty.  I've used it myself to seal around the base of outdoor electrical fixtures.  Even after 25 years, it is still pliable.

 

[userone]

the duct seal is what you want, it is like clay that is a little greasy, I can confirm it stays soft forever and you could cover a pretty big hole with it.

 

[NeverDie]

Electricians often use this stuff, called Duct Seal.  It's a heavy duty waterproof putty.  I've used it myself to seal around the base of outdoor electrical fixtures.  Even after 25 years, it is still pliable.

 
Awesome!  Sounds easy, cheap, fast, and time-tested, so despite what I wrote in post #6, I think I'll give it a go.
 
Thanks, RAL, and thanks userone also!

 

[Del91574]

If you're mounting it inverted on a soffit and not a facia...there is really no need to gasket the unit to the concrete backer! Water doesn't flow up and the substrate isn't going to deform like vinyl or other materials.

 

[NeverDie]

If you're mounting it inverted on a soffit and not a facia...there is really no need to gasket the unit to the concrete backer! Water doesn't flow up and the substrate isn't going to deform like vinyl or other materials.

 
You raise a good point.  There's probably an architectural term for the kind of soffit the videocam will be hanging from, but I'll just show it in a picture (below).   It seems to be more decorative than functional, and, unlike a vented attic, it is a hollow, unvented and uninsulated compartment that does not connect with anything, not even the attic.  It's on a gable wall.
 
So, the question is: would putting a 1-1/2" hole in such a soffit allow high humidity to enter and, over time, adversely affect the mostly wooden interior?  Anyone know?  I don't know what building science model to reference for that scenario, but I do know the local climate often has abundantly high humidity, with recurring and sometimes extended stretches of 90%+ RH.   Anyhow, not knowing the answer, I thought it safest to keep it sealed, nearly the same as it had been.  I cut a hole through the interior wall, and then cut another through the OSB sheathing so that I could run the cat6 to the interior of the cavity and ultimately through a hole (yet to be drilled) in the soffit.  I had a look inside, and at least so far it seems to be holding up well the way it was built as a sealed cavity.

 

[NeverDie]

Here's a photo of the soffit taken from the other direction.
 
It's worth resolving, if possible, because if this first trial goes well, I may be installing more of the same camera on similar soffits elsewhere on the house.

 

[NeverDie]

Here's the drilling template.

 

[RAL]

Unless you were to hermetically seal that space, humidity in the air is going to get in there no matter what over a period of hours and days through small gaps between the construction materials.  So I wouldn't worry too much about the effect that drilling a few holes in the soffit will have.  In fact, having the holes in the soffit might make it slightly easier for moisture that does get in there to escape when it becomes less humid outside.
 
If you want to seal things up, it won't make anything worse than it was before drilling the holes.  I would probably do it more to keep any insects from finding a way into the house.   If you were going to mount the camera on the side of the house rather than on the bottom of the soffit, then I think sealing it would be more important for keeping water out.

 

[NeverDie]

Unless you were to hermetically seal that space, humidity in the air is going to get in there no matter what over a period of hours and days through small gaps between the construction materials.  

 
That type of vapor drive undoubtedly does happen to one degree or another, but the rate at which it happens is apparently slow enough that it's offset by drying through the OSB sheathing into the drier stud bay and materials on the opposite side.  I can't say for sure, but that may be part of the theory behind it.  For instance, it would explain why there's no Tyvek or other vapor barrier covering that particular section of the OSB wall sheathing.
 
Mitigating insect intrusion is potentially another good reason to seal it, as you point out.
 
All that said, I'm open to having my mind changed about it.